This invention relates to planetariums and, in particular, to a portable planetarium having the shape, structure, and utility of an extended umbrella while serving the dual and more important function of being an educational tool usable to ascertain the location of planets and stars throughout the year.
Devices utilizing umbrella shaped domes to designate a portion of the sky and the stars contained therein were first proposed many years ago. U.S. Pat. No. 1,150,731 to Barcus discloses a star finder in the shape of a parasol on which stars and certain constellations are marked to be used as a guide in finding their location in the sky. The structure of Barcus' umbrella, however, limits his device to being able to depict accurately only a very small portion of the sky in that the common parasol which Barcus utilizes emcompasses less than a full hemisphere.
This design proves disadvantageous in that the ecliptic, the path along which the sun travels in the sky in relation to the stars, may not be accurately shown upon a hemisphere using Polaris as a polar reference. Since the ecliptic may not be accurately depicted upon a parasol such as utilized in Barcus, it is impossible for such a device to accurately depict the position of the planets throughout the course of the year, for the planets travel with the sun through the sky. British Pat. No. 342,886 to Grone discloses a similar device for teaching astronomy. Grone's device also includes less than 90.degree., or less than a full hemisphere, and therefore Grone again could not accurately depict the full ecliptic without distortion. Grone fails to disclose, thereby, a portable planetarium, but rather proposes a partial star map to be utilized in certain locations in depicting only certain constellations. Both Grone and Barcus suffer the common disadvantage of being unable to accurately depict the full ecliptic thereby precluding their use to trace the path of the planets during the course of the entire year.
It should also be understood that since the devices disclosed in Barcus and Grone utilize an ordinary parasol or umbrella, they must be viewed from outside of the umbrella. Therefore, while they provide some added dimension, their effect is not unlike that of viewing a portion of the sky depicted on a flat star map.